U.S. Pat. No. 2,654,993 to Owner is concerned with gas turbine engines, each comprising a main turbine having a pair of rotating rotors through which gas is passed in succession and an auxiliary turbine to drive the engine which is driven by gasses drawn off from the rotors of the main turbine. Each engine comprises an axial-flow compressor, combustion equipment, and an axial flow turbine having a pair of independent rotors through which the combustor gas is passed in succession. More particularly, gas is bled from between the high and lower pressure turbines, respectively. This bled gas powers an auxiliary turbine which may be used to power an auxiliary engine and/or aircraft accessories.
U.S. Pat. No. 3,867,813 to Leibach is directed to a turbine engine having an additional fan, burner and turbine to increase power during takeoff and landing. These added components are not intended for operation at other flight conditions.
U.S. Pat. No. 4,206,593 to Su et al describes a gas turbine comprising an air compressor, one or more combustion chambers, and one or more expansion turbines. The air compressor, the combustion chambers and the turbines can be placed on one shaft or on separate shafts so long as the gasses flow in a direction from the compressors to the combustion chambers and then to the turbine.